570 



ALEXANDER W. EVANS 



*I2. R. leptostachya nov. spec. — Fig. 4. 



Growing in velvety but somewhat depressed mats, dull green becoming 

 brownish with age, more or less translucent: thallus consisting of a prostrate 

 axis giving off ascending branches and prostrate stolons, the axis flattened and 

 often with a wing one or two cells wide; ascending branches mostly simple but 

 sometimes sparingly subdivided, more strongly flattened than the axis, the 

 marginal wings being two or three cells wide and crenulate: inflorescence dioi- 

 cous: J* inflorescences arising singly, not recurved, the wing crenulate, erect 

 or incurved; antheridia mostly ten to twenty: $ inflorescence occupying a very 

 short branch; involucre consisting of a series of short and irregular cilia or 



Fig. 4. Riccaj-dia leptostachya Evans. 



A — C. Parts of thalli of various types, X i4- D. Transverse section of prostrate axis, X 100. 

 E. Transverse section of an erect branch, x 100. F. Male brancli, dorsal view, X 100. G. Fe- 

 male branch with young sporophyte, X 50. The figures were all drawn from the type specimen. 



laciniae, three to five cells long; calyptra smooth or nearly so, the corona in- 

 conspicuous: sporophyte not seen. 



On decayed wood, 260 m. and below. 



Masatierra: V. Anson, near Plazoleta, on decayed timber, 260 m. (no. 

 41); Q. Juanango, on logs in river bed (no. 42). No. 42 may be designated 

 the type. 



In R. leptostachya the differentiation in the branches, which is rather 

 vaguely indicated in R. variabilis, is more completely realized, although it still 

 falls short of the definite differentiation found in certain other members of the 

 genus. The thallus in other words, shows a prostrate axis with long-continued 

 growth, giving rise to ascending photosynthetic branches and prostrate stolons. 



